Dimethyl carbonate is advantageously used as a starting material in the synthesis of a polycarbonate, a plastic engineering material, and is also advantageously used as a solvent and as a reactive material when producing various chemical products such as secondary battery electrolytes, and, paints. Dimethyl carbonate has been produced through a variety of methods, and among these methods, research into a method of producing dimethyl carbonate via a reaction between urea and methanol, in which relatively inexpensive raw materials are used, has been actively undertaken.
Relatively low concentrations of dimethyl carbonate, e.g. less than about 25% by weight, may often be present in a mixture with methanol. In particular, dimethyl carbonate can be obtained from a mixture thereof with methanol using a variety of methods for producing dimethyl carbonate. Dimethyl carbonate and methanol form an azeotropic composition having a dimethyl carbonate to methanol weight ratio of about 30:70 at atmospheric pressure.
Thus, high purity dimethyl carbonate, e.g. well over 99% by weight, is required to be separated from a mixture containing dimethyl carbonate and methanol. Since dimethyl carbonate and methanol form an azeotrope, the efficient separation thereof may not be obtained through a general separation process, and thus, a specific separation process is applied thereto. Here, for example, a pressure swing distillation method, a high pressure distillation method, and an extractive distillation method may be used.
The extractive distillation method is a method for separating a mixture component representing azeotropic behavior. In an extractive distillation process, an extractive distillation agent changes a degree of relative volatility of components of a mixture so as to form a sufficient volatility differential, such that an effective separation through distillation may be obtained. However, there is a problem in that an additional distillation process to re-separate the extractive distillation agent and dimethyl carbonate from each other is required, and such a process may result in a relatively low dimethyl carbonate recovery rate, and high energy consumption and high investment costs due to the application of multiple columns.
Meanwhile, in the case of the pressure swing distillation method, operating costs may be increased, based on high-pressure operations and large recycle streams leading to increased equipment sizes, and found to be uneconomical.